Orange County North Basin

Overview

A contaminated groundwater plume sits beneath parts of Anaheim, Fullerton, and Buena Park in Orange County, California. Industrial spills and leaks over several decades left chlorinated solvents, including tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene (1,1-DCE), and 1,4-dioxane, in soil and groundwater. EPA also is evaluating perchlorate and perfluorinated compounds at the site. Five drinking water wells in Fullerton and Anaheim have been taken out of service because of contamination. Groundwater supplies about 85 percent of Orange County's water and serves roughly 2.4 to 2.5 million residents across 22 cities. Water purveyors closely monitor the supply, and drinking water delivered to consumers currently meets federal and state standards.

EPA added the site to the National Priorities List (NPL) on September 3, 2020, after an initial assessment on June 29, 2017. The Orange County Water District (OCWD) and EPA entered an administrative agreement in October 2016 to complete a remedial investigation (RI) and feasibility study (FS). OCWD finished the RI in June 2022 and the FS in August 2025. The site is divided into three operable units: a sitewide unit, an Interim unit, and a Regional Aquifer Plume unit. For the Interim unit, the combined RI/FS was completed in November 2024, and a Record of Decision (ROD) is estimated between September and November 2026. For the Regional Aquifer Plume unit, the RI is estimated to finish between September and November 2027, and a ROD is estimated for September through November 2028.

EPA released a Proposed Plan to contain and treat contaminated groundwater. A public comment period ran from January 5, 2026, to March 23, 2026. EPA is now preparing a ROD, the formal final cleanup plan, along with a Responsiveness Summary addressing public comments. EPA is also reviewing state files and historical documents to identify companies that may be responsible for performing or funding the cleanup. Physical cleanup construction has not yet started, and groundwater migration is not stabilized.

Community members can get involved in several ways. A Community Advisory Group (CAG) has not yet been formed at this site. A CAG brings together local stakeholders to share concerns and provide input during cleanup. Anyone interested in helping form a CAG can contact the EPA Community Involvement Coordinator. The public will be notified when the ROD is complete.